Lamp socket diodes and 555 lamp boards
On #44/#47 sockets the diode band goes to the middle (side) lug and the non-banded end to the lamp tip lug. #555 bulbs sit on small lamp boards with the diodes on the board; the Molex header pins soldered on the back of those boards often crack, and the small tabs on #555 sockets bend and lose contact (bend them back).
Systems
Related tips
- Testing a lamp diode in place
- Testing lamp matrix columns with a test socket
- Testing lamp matrix rows with a test socket
- One lamp dead though socket and wiring are good: diode on the lamp board
- Single matrix lamp out with good bulb and wiring
- System 11 lamp matrix
- #555 and #259 wedge lamps
- An entire lamp row or column is out
Source: Repairing Williams System 11 Pinball 1986 to 1990, Part Two, Clay Harrell (pinrepair.com)